Fast 30400-KIT-EZ-EF Instructions Manual - page 33
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disabling it. Keep in mind that it is normal for the EZ-EFI
®
system’s “pre-squirt” feature
(discussed in the EZ-EFI
®
SYSTEM FEATURES section) to pulse the injectors for a second
or two right at key-on. This feature can be distinguished from a potential ignition issue in
several ways:
The “pre-squirt” feature will inject a measured amount of fuel – it will not come
anywhere near flooding the engine.
The “pre-squirt” feature will not continue to occur on subsequent key cycles unless
the engine has been started.
The “pre-squirt” feature will not cause the blue CRANK/DIAG LED on the face of
the ECU to come on solid when the engine isn’t running as a false RPM signal
would. It also won’t cause a tachometer to display a non-zero RPM value.
2. Inductive coil – Another source for an RPM signal is the negative side of the ignition coil in
a traditional dwell-controlled inductive ignition system. This is one in which the coil is fed
power on one side and is charged by grounding the other side – either by “points” or some
form of electronic module. A standard, unmodified HEI is one example of this type of
ignition system.
To use this RPM signal option, the RPM Module is required. The RPM Module connects to
the negative side of the coil and outputs a “Tach” signal to the ECU. The RPM Module is
connected as follows:
WIRE COLOR
CONNECTION
Black
Engine block
Black
Engine block
White
Negative side of coil
Yellow
“RPM INPUT” wire in wiring harness
The RPM Module is provided to allow this convenient installation option. But keep in mind
that it has limitations. The negative side of an ignition coil is one of the noisiest points on the
engine. There are large voltage spikes and ringing when the coil fires. Different coils will have
different noise characteristics. And this noise can change as the engine runs. Anything that
affects how hard the coil has to work to fire the spark plug – changing cylinder pressure, worn
plugs or plug wires, etc. – will affect this signal.
In most applications, the RPM Module will be able to deal with these challenges and feed a
clean RPM signal to the ECU. But the old saying – garbage in, garbage out – applies here. If
the inductive ignition system is just too noisy or inconsistent, it may need to be abandoned in
favor of an aftermarket ignition box.
RPM Module Installation Notes:
HEI distributors (and possibly others) have a terminal labeled “TACH”. However, that is not a
clean digital tach signal like an aftermarket ignition box would supply. Instead, it is simply
another terminal connected to the negative side of the coil. Do NOT connect the “RPM